I agree with everything you said. Didn't know the old MS cleaner was pitched, but stopped using it anyway.. Ms usually has a [fix-it] tool for a lot of problems now. Just googling many problems leads to these. Probably the smartest thing Redmond has done in a long time.
I notice the one time I did a CCleaner analysis of my x64 Vista registry it found nothing, and usually does. If it ever does I shall not try to fix it unless problems come up later. Getting rid of unsigned drivers may be part of the improvement here.
CCleaner is more valuable for virus or malware after action as far a the registry goes on Vista, it seems to me. Over all it is even more valuable for simply cleaning up temp files and such that hold misbehaving files that slow or stop my surfing in Internet Explorer. Using several other security applications has made this more unnecessary all the time.
Spyware Blaster shuts down bad server request that can place malicious ads or malware into the machine, also keeps bad active x vectors from jumping the web page and installing.
I'm not sure how AdAware makes a difference in this area, as I don't use AdWatch, but updating it seems to speed surfing up immediately, I'm not sure if it uses host files or not. Malwarebytes Anti-malware has a process guard that I am evaluating now, and it shows no conflict with NIS 2009 so I'm sure it will work with ESET or AVAST successfully too.
But I still use the regular cleaner on CCleaner at least once a week when nothing else works. Apparently it simply gets rid of misbehaving(malicious?) temp files that are not capable of installing on 64 bit Vista systems.
This has been the easiest most effective way to speed browser performance for me; not registry cleaning.